bdl wrote:

Studies have shown that napping improves performance after the nap.

In the article that I read, the FAA said that the napping had a
detrimental affect on performance. It meant the controllers were
groggy when returning to the scope.

So maybe the FAA has their own study.

From what I've read, short naps are ok, but anything longer than 15-20
minutes is detrimental.